On 29 March 2018 at 11:54, Peter Maydell <peter.mayd...@linaro.org> wrote: > On 23 March 2018 at 12:08, Peter Maydell <peter.mayd...@linaro.org> wrote: >> On 21 March 2018 at 08:00, Shannon Zhao <zhaoshengl...@huawei.com> wrote: >>> On 2018/3/20 19:54, Peter Maydell wrote: >>>> Can you still successfully migrate a VM from a QEMU version >>>> without this bugfix to one with the bugfix ? >>>> >>> I've tested this case. I can migrate a VM between these two versions. >> >> Hmm. Looking at the code I can't see how that would work, >> except by accident. Let me see if I understand what's happening >> here:
> I was thinking a bit more about how to handle this, and > my best idea was: > > (1) send something in the migration stream that says > "I don't have this bug" (version number change? > vmstate field that's just a "no bug" flag? subsection > with no contents?) > > (2) on the destination, if the source doesn't tell us > it doesn't have this bug, and we are running KVM, then > shift all the data in the arrays down to fix it up > [Strictly what we want to know is if the source is > running KVM, not if the destination is, but I don't > know of a way to find that out, and in practice TCG->KVM > migrations don't work anyway, so it's not a big deal.] Shannon, are you planning to look at this for 2.12, or should we postpone it to 2.13? (It's not a regression, right? So we don't necessarily have to urgently fix it for 2.12.) thanks -- PMM
